Electrostatic Field Distribution Research Articles

Modeling and Experimental Verification of TIGBT Detailed Internal Electric Fields Which Lead to Breakdown

Distribution and intensity of electrostatic field in a trench insulated gate bipolar transistor, a key factor in the breakdown of such power semiconductor devices, are investigated using the variational thermodynamic methodology based on device Helmholtz free energy yielding closed-form solutions. Attention is given to quantifying the detailed field effects due to curvature near the bottom of the gate. Our modeling of the bottom edge of the gate uses the shape of a published scanning electron microscopy image of an as-built trench gate. This necessitates an appropriate approach to represent subtle details of the system. We have also examined the modification of electrostatic field and potential in that region due to oxide charge. The electrostatic field is quantified and described for sheet charges of variable polarity, intensity, and position in the oxide. We have employed Fermi–Dirac statistics instead of Boltzmann statistics, which underconstrain mobile electron and hole populations at the operating conditions of the device studied. Our model results are consistent with the device gate breakdown experiments.

Droplet formation and settlement of phase-change ink in high resolution electrohydrodynamic (EHD) 3D printing

This paper presents a modeling framework to model the droplet formation and settlement on substrate of phase-change ink in high resolution electrohydrodynamic (EHD) printing process, which can successfully produce sub 10-μm droplet footprints and 3D microstructure. We have used Finite Element Analysis (FEA) to develop the model for droplet formation and droplet settlement. Two important competitive forces in EHD printing, electrostatic force and surface tension force are modeled by FEA. The droplet size is obtained by balancing the electrostatic force and surface tension of the pending droplets at the tip of the meniscus under different printing conditions. With the results from FEA analysis about the charge on a droplet and electrostatic field distribution, the droplets in-flight velocity and impact velocity on the substrate are derived numerically. With the derived impact velocity, the droplet spreading and settlement on the substrate is also modeled by FEA. The results from FEA models are compared with the experimental measured droplet dimensions at different process conditions to validate the developed model, which demonstrate very good agreement between the experimental results and model prediction. We have successfully applied EHD printing process for phase-change wax material, which is widely used in 3D printing or additive manufacturing for supporting and model material, to achieve high resolution sub 10-μm 3D structures.

Potential‐based threshold voltage and subthreshold swing models for junctionless double‐gate metal‐oxide‐semiconductor field‐effect transistor with dual‐material gate

SummaryOn the basis of quasi‐two‐dimensional solution of Poisson's equation, an analytical threshold voltage model for junctionless dual‐material double‐gate (JLDMDG) metal‐oxide‐semiconductor field‐effect transistor (MOSFET) is developed for the first time. The advantages of JLDMDG MOSFET are proved by comparing the central electrostatic potential and electric field distribution with those of junctionless single‐material double‐gate (JLSMDG) MOSFET. The proposed model explicitly shows how the device parameters (such as the silicon thickness, oxide thickness, and doping concentration) affect the threshold voltage. In addition, the variations of threshold voltage roll‐off, drain‐induced barrier lowering (DIBL), and subthreshold swing with the channel length are investigated. It is proved that the device performance for JLDMDG MOSFET can be changed flexibly by adjusting the length ratios of control gate and screen gate. The model is verified by comparing its calculated results with those obtained from three‐dimensional numerical device simulator ISE. Copyright © 2015 John Wiley & Sons, Ltd.

Study on charge storage characteristics of PP film electret charged by interface polarization method

Electret attracts increasing attention nowadays because of its lasting and stable electrostatic field. To achieve the widespread use of electret material, higher density and better stability of the electret charge storage as well as well-distributed electrostatic field must be ensured at the same time. Based on the mechanism of interface polarization on double-layer media, a novel charging technology for electret is reported in this paper; and PP film is successfully charged through an auxiliary layer to form electret by this proposed method. Effect of charging temperature and charging voltage on the charge storage performance of the as-prepared PP film electret is investigated by means of surface potential measurement. Also its charge storage performance at high temperatures is explored by thermally stimulated discharge technique. Furthermore, its electrostatic field distribution in the directions of X and Y is measured. Results show that the interface polarization charging is more excellent than the corona charging. At a certain temperature, the surface potential of PP film electret increases with increasing charging voltage and both are in a good linear relationship. This is in good agreement with the theoretical analysis in terms of the equation of electret charge accumulation during the charging process. It is shown that in the case of constant charging voltage within the range of 0.53.0 kV, the effect of charging temperature is not obvious when the temperature is below 75 ℃; however, when the temperature is higher than 75 ℃, the surface potential of PP film electret increases with increasing temperature. In addition, its surface potential may change a little with time so it has an excellent charge storage stability. The distribution of its surface potential shows that it exhibits an homogeneous electrostatic field due to interface polarization charging.

2D Asymmetric Silicon Micro-Mirrors for Electrostatic Field Distribution Measurement Using Optical Level Method

We developed silicon micro-mirrors with two asymmetric axes for electrostatic field distribution measurements using a single external piezoelectric ceramic vibrating element. The 2D asymmetric silicon micro-mirrors were fabricated by using an SOI-MEMS process. The vibration transmissibility of the proposed mirror under a vacuum atmosphere was evaluated by dynamic analysis. We obtained the resonant frequency in the low-speed axis of 23.3 Hz and in the high-speed axis of 556.8 Hz respectively. To prevent a reduction in the amplitude width, we induced a 90° phase shift between the lowand high-speed axes at the resonance frequency. The ratio of the deformation between the low-speed axis of 30 Hz and the high-speed axis of 604 Hz was simulated to be 4.04. In measurement, the ratio of the deformation between the low-speed axis of 23.3 Hz and the high-speed axis of 556.8 Hz was 6.48. The difference between the calculated and experiment values were apparently due to the fabrication errors and frequency characteristics of piezoelectric ceramic vibrating element. A Lissajous pattern projected onto the screen. The scanning angle was a degree of 7.6 (total angle) in the lowand high-speed axis. We subsequently measured the electrostatic field distribution using the 2D asymmetric silicon micro-mirrors by means of the optical level method.

Preparation and charge storage property of FEP thin film electret with grid electric field distribution in millimeter scale

Electret has caught wide attention because it can produce a lasting and stable electrostatic field in the application of MEMS devices such as miniwatt electret generator, electret motor, electret sensor, electret transducer, and so on. Of all the above applications, a remarkable feature is that the electrostatic field distribution on electret surface is patterned in millimeter size or even smaller. However, the charge storage performance of electret in miniature size will dramatically get worse in contrast with the macro-electret. Therefore, it is very important to develop an applicable preparing method to maintain the stability of electrostatic field distribution in micro-patterned electret. In this paper, it is reported that a fluorinated ethylene propylene copolymer (FEP) with evaporated aluminum grid electrode a 25 m thickness topped with at a step of 2 or 3 millimeter are successfully prepared to form the electret with well grid distribution of electric field(abbreviated as grid electret) by means of corona charging and thermal charging technology. Effect of grid width and charging temperature on the charge storage performance is studied. After stored for 150 days, the grid distribution of electric field on the FEP surface becomes clear and organized. The potentials of the area covered by aluminum electrode are close to zero, while that of uncovered area still remain high. The potential differences between the covered and uncovered by aluminum electrode area are identical in different charging methods, it is 110 V (electric field 44 kV/cm) for the sample with an electrode width of 2 mm, and 130 V (electric field 52 kV/cm) for the sample with an electrode width of 3 mm. Results also show that the initial surface potentials of the grid electrets prepared by corona charging is higher than that by thermal charging, but the former decays more rapidly. For the same charging method, the narrower the aluminum electrode area can lead to the lower initial surface potential, and the higher charging temperature causes the larger initial surface potential. According to the principle of corona charging and thermal charging technology it is concluded that the difference of charge storage capability between FEP and aluminum can account for the grid distribution of electric field on the FEP surface.

非链式脉冲氟化氘激光器的放电特性

In order to enhance the non-chain DF laser output energy and electro-optic conversion efficiency,the electrostatic field distribution of Chang electrode and flat electrode which was consisted by rough cathode and smooth anode was calculated by finite element method. For Chang electrode,the higher electric field of spark-pin was introduced,and the electrostatic field distribution of sparkpin UV pre-ionization was calculated. For the flat electrode,the electrostatic field distribution of burr on the cathode surface was calculated. The burrs on the cathode surface can form a series of higher electric field,but can't lead to uniformity of plate electrode field deteriorating. And then,pulsed discharge experiments were carried out on two kinds of electrodes,so discharging performance and output characteristics of non-chain pulsed DF laser were obtained. The discharge experiment results show that the uniform electric field is conducive to increase the output energy of nonchain pulsed DF laser. It is also verified that the higher electric field of the burrs on the cathode of self-initiated discharge DF laser is benefit to volume discharge. Besides,the self-initiated discharge is more applicable for large volume discharge.

Towards quantitative electrostatic potential mapping of working semiconductor devices using off-axis electron holography.

Pronounced improvements in the understanding of semiconductor device performance are expected if electrostatic potential distributions can be measured quantitatively and reliably under working conditions with sufficient sensitivity and spatial resolution. Here, we employ off-axis electron holography to characterize an electrically-biased Si p-n junction by measuring its electrostatic potential, electric field and charge density distributions under working conditions. A comparison between experimental electron holographic phase images and images obtained using three-dimensional electrostatic potential simulations highlights several remaining challenges to quantitative analysis. Our results illustrate how the determination of reliable potential distributions from phase images of electrically biased devices requires electrostatic fringing fields, surface charges, specimen preparation damage and the effects of limited spatial resolution to be taken into account.

The Influences of Interdigitated Electrode Asymmetry on the Actuation Performance of Piezoelectric Materials

The electrostatic field distribution of interdigitated electrode piezoceramics (IDEPZT) and piezoelectric fiber composite (IDEPFC) are analyzed by finite element method separately. The impact of the interdigitated electrode asymmetry on the actuation performance of piezoelectric actuators with a certain interlayer thickness is studied. The influence of the interdigitated electrode asymmetry on the actuation performance, stress concentration and electrostatic field concentration with different interlayer thicknesses are also discussed and compared. For piezoceramics, the results show that the actuation performance can be influenced little by increasing the degree of the excursion with a relatively thin interlayer thickness. As the interlayer thickness increases, the actuation performance can be influenced much by increasing the degree of the asymmetry. And it results in the decrease of the longitudinal free strain overall. The electric field becomes increasingly uneven as the degree of the asymmetry increases. The actuated stress can be improved evidently by increasing the degree of the asymmetry with a relatively thin interlayer thickness while the stress concentration is not increased apparently.

Multi-needle, electrospun, nanofiber filaments: effects of the needle arrangement on the nanofiber alignment degree and electrostatic field distribution

Nanofiber filaments were produced by a home-made, multi-needle, liquid bath, electrospinning device, and the nanofiber alignment degrees of the filaments were investigated. The electrostatic fields of the multi-needle, liquid bath, electrospinning processes were simulated by the finite-element method, and an index, the average offset of the electrostatic field distribution in the needle tips, was established to quantify the existing electrostatic field interference. The effects of the number and the arrangement of the needles on the alignment degrees of the nanofibers and the breaking stress of the filaments were analyzed. The results showed that there was a linear negative correlation between the nanofiber alignment degrees and the number of needles with an R2of 0.96. The larger average offset indicated the stronger electrostatic field interference, and a logarithmic positive correlation was determined between the average offsets and the number of needles with an R2of 0.99. There was a linear negative correlation between the nanofiber alignment degrees and the average offsets with an R2of 0.97. Meanwhile, when the average offsets in different numbers of needles increased from 0 to 0.160 mm, the average alignment degrees decreased from 0.964 to 0.774. Therefore, the optimal needle arrangement with the lowest average offset for each number of needles could be obtained. In addition, the breaking stress of the filaments decreased with the increase of the average offsets in the same number of needles, and the average breaking stress decreased initially with increasing the number of needles until three needles and then increased.

Fabrication of a flexible Ag-grid transparent electrode using ac based electrohydrodynamic Jet printing

In the dc voltage-applied electrohydrodynamic (EHD) jet printing of metal nanoparticles, the residual charge of droplets deposited on a substrate changes the electrostatic field distribution and interrupts the subsequent printing behaviour, especially for insulating substrates that have slow charge decay rates. In this paper, a sinusoidal ac voltage was used in the EHD jet printing process to switch the charge polarity of droplets containing Ag nanoparticles, thereby neutralizing the charge on a polyethylene terephthalate (PET) substrate. Printed Ag lines with a width of 10 µm were invisible to the naked eye. After sintering lines with 500 µm of line pitch at 180 °C, a grid-type transparent electrode (TE) with a sheet resistance of ∼7 Ω sq−1 and a dc to optical conductivity ratio of ∼300 at ∼84.2% optical transmittance was obtained, values that were superior to previously reported results. In order to evaluate the durability of the TE under bending stresses, the sheet resistance was measured as the number of bending cycles was increased. The sheet resistance of the Ag grid electrode increased only slightly, by less than 20% from its original value, even after 500 cycles. To the best of our knowledge, this is the first time that Ag (invisible) grid TEs have been fabricated on PET substrates by ac voltage applied EHD jet printing.

The Calculation and Experiment Based on the Finite Difference Method for the High-Voltage Electrostatic Field of Melting Electron Beam Gun

Aiming at high voltage electrostatic field of melting electron beam gun system, taking 30 kv 60 kw melting electron beam gun for example, the structure of the electric field and boundary conditions was designed. And the mathematical model of the electric field was established. The method of numerical calculation was used to solve the mathematical model, and Matlab software was used to simulate the equipotential lines of the electric field. The electrolytic cell experiment was used to simulate high voltage electrostatic field distribution of the electron beam system. At the same time compared with the two different results, the reasons and the improved method were analyzed. For research and calculation high voltage electrostatic field of processing equipment such as electron beam welding, melting, etc, offers a more general analysis, design and calculation methods.

Drop-on-demand E-jet printing of continuous interconnects with AC-pulse modulation on highly insulating substrates

In this paper, we present a novel AC-pulse modulated electrohydrodynamic (EHD) jet printing technology that enables high resolution fabrication of electrical features and interconnects using the silver nanoink on highly insulating substrates. In traditional EHD jet printing, the remained charge of the printed droplets changes the electrostatic field distribution and interrupts the follow-on printing behavior, especially for highly insulating substrates having a slow charge decay rate. In this paper, a modulated AC-pulsed voltage was used for the EHD jet printing process that can alternate the charge polarity of the consequent droplets to neutralize the residue charge on the substrate. The effect of the residue charge is minimized, which enables high resolution printing of continuous patterns. With three printing parameters (e.g. pulse frequency, voltage, and duration), the EHD jet printing speed and droplet size can be controlled independently. We demonstrated that AC-pulse modulated EHD jet printing can overcome the charge accumulation challenge on highly insulating substrates, and investigated the variables of fabrication process to achieve reliable jet printing of conductive silver tracks.

Subthreshold behavior models for nanoscale junctionless double-gate MOSFETs with dual-material gate stack

By using a variable separation technique, an analytical model of the two-dimensional (2D) channel electrostatic potential for junctionless dual-material double-gate (JLDMDG) MOSFETs is derived from the 2D Poisson’s equation. On the basis of the 2D channel electrostatic potential and the current continuity equation, a subthreshold current model is obtained. The advantages of JLDMDG MOSFETs are proved by comparing the central electrostatic potential and electric field distribution with those of junctionless single-material double-gate (JLSMDG) MOSFETs. In addition, the influence of different device parameters (such as body thickness, oxide thickness, and the ratio of gate length) on subthreshold current and subthreshold slope is investigated. It is found that a smaller body thickness or gate oxide thickness or a longer control gate induces a better subthreshold performance. The data extracted from the developed model are in good accordance with simulation results obtained from DESSIS.

High-resolution ac-pulse modulated electrohydrodynamic jet printing on highly insulating substrates

This paper presents a new high-resolution ac-pulse modulated electrohydrodynamic (EHD)-jet printing technology on highly insulating substrates for drop-on-demand fabrication of electrical features and interconnects using silver nanoink. In traditional EHD-jet printing, the remained charge of the printed droplets changes the electrostatic field distribution and interrupts the follow-on printing behavior, especially for highly insulating substrates which have slow charge decay rates. The residue charge makes the control of EHD-jet printing very challenging for high-resolution continuous features. In this paper, by using modulated ac-pulsed voltage, the EHD-jet printing process switches the charge polarity of the consequent droplets to neutralize the charge on the substrate. The effect of the residue charge is minimized, which enables high-resolution printing of continuous patterns. Moreover, by modulating the pulse frequency, voltage, and duration, the EHD-jet printing behavior can be controlled with respect to printing speed/frequency and droplet size. Printing frequency is directly controlled by the pulse frequency, and the droplet dimension is controlled by the voltage and the duration of the pulse. We demonstrated that ac-pulse modulated EHD-jet printing can overcome the long-predicated charge accumulation problem on highly insulating substrates, and potentially be applied to many flexible electronics applications.

Electrostatic Field Distribution Measurement Using MEMS Micro-mirror Array

Electrostatic field distribution measurement using a silicon micro-mirror array fabricated by Micro-Electro-Mechanical Systems (MEMS) process has been presented. The deflection angle of each micro-mirror, which is placed on a spherical surface and is deflected by electrostatic field, was measured optically using a two-dimensional optical scanner and a position sensitive detector (PSD). The obtained electrostatic data showed good agreement with Coulomb's law and the system was applied to measure the electrostatic field distribution of charged substance.

Optimization of a Triggered Vacuum Switch With Multirod Electrodes System

The breakdown and triggering characteristics of triggered vacuum switch (TVS) are very important features, and they affect the operation reliability of TVS. Both of them mainly depend on the electrode material, electrode shape, gap distance, and surface condition. For an optimized electrode's geometry, finite-element method electrostatic field simulations were conducted to evaluate the effect of geometric parameters on the electrostatic field strength and distribution. The distribution of electrostatic field of the TVS with multirod system (MTVS) is calculated by the finite method. The simulation results show that the geometric enhancement factor (GEF) is decreased with the increase of the fillet radius of the edge of the rod. In case of the fillet radius for the side face of rod 3 mm and the fillet radius of the top face of the rod is 5 mm, the GEF is decrease to a minimum value of 3. The breakdown voltage of MTVS was measured by the high-voltage direct current generator after switch currents with amplitude of 63 kA and width of 13 ms with the interval time of 10–15 min. The influences of electrode materials and operation times on the breakdown voltage and trigger characteristics are also studied. The experimental results show that the breakdown voltage of the optimized MTVS is higher than that of the non-optimized MTVS. The breakdown voltage of CuCr30 is higher than that of oxygen-free copper. In addition to, the trigger characteristics of MTVS are influenced mainly by the electrode materials, the fillet radius of electrode has a little effect on the triggering characteristics of MTVS.

An analytical approach for scanning probe microscope-tip electrostatic field distribution accounting for dead layer and domain wall

We have proposed a new theoretical approach for the determination of the electric field distribution in the ferroelectric/dielectric system with the presence of the SPM tip. The initial statement of the model has only a numerical solution. To find an analytical solution of the problem, some assumptions are introduced: the domain wall thickness can be considered to be much smaller than the domain size, and we use a high ferroelectric dielectric permittivity. The developed approach allows us to obtain explicit formulas for the polarization and electric field intensity. We have calculated and then analyzed the tip capacitance as a function of the distance from the ferroelectric interface. Additionally, different forms of the SPM tip are considered. It is demonstrated that in the presence of charges at the domain, the results differ from those obtained with the widely used dielectric model by 30%.

A New Set of Electrodes for Coaxial Quarter Wave Switched Oscillators

We present a new profile for the electrodes forming the radial transmission line of a switched oscillator (SWO). The profile is formed using a curvilinear orthogonal space based on a specific 2-D transformation called logarithmic-tangent. The proposed profile results in an optimal distribution of the electric field, with a peak amplitude occurring on the axis of symmetry of the SWO, and a smooth, monotonic decrease in amplitude, as we move away from the discharge point toward the coaxial transmission line. In addition, the proposed profile assures a smooth continuity at the junction of the radial transmission line-coaxial line. Numerical simulation results on the electrostatic field distribution in the SWO are presented and discussed.

Neural Network based Electrostatic Fields Distribution Modeling for Harmattan Season in Zaria, Nigeria

This paper presents the application of neural network to the electrostatic field distribution modeling using harmattan season data in Zaria, Nigeria. The data was captured through an on-line mechanism for twenty-four months by the computer using the Microsoft Office Excel Program for twenty-four months (February, 2007 - February, 2009). The focus of the analysis is determining the effect of environmental factors such as temperature, pressure and relative humidity on the static electric field during the harmattan season. The plots of the electrostatic field against the variation of the environmental factors were used as the qualitative analytical tools and yielded a non-linear relationship. The data was analyzed using Neural Network version 3.24 Software, to establish predictive models for Harmattan outside and inside Scenarios. The result of the analyses yielded good neural statistical values of Root Mean Square Error (RMSE) of 0.09, and Pearson R value of 0.76 for outside Scenario. Similarly for Harmattan inside Scenario, gives a RMSE value of 0.14, and Pearson R value of 0.77 respectively, which are reflections of a good model. The result was further buttressed by the plot of the Neural Network based Electrostatic Fields distribution modeling of the experimental and the predicted parameters. With the insignificant values of the RMSE, Pearson R value which are reflections of the closeness of the predicted and the experimental parameters, hence the could be relied upon to predict the electrostatic fields during harmattan in Zaria, Nigeria.